1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly, to a liquid crystal display panel and a method of fabricating the same that are capable of simplifying a fabricating process and forming a spacer at a desired location.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device controls the light transmittance of liquid crystal cells using an electric field, to thereby display a picture. To this end, the LCD device includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix, and driving circuits for driving the liquid crystal panel. The liquid crystal display panel is provided with pixel electrodes and a reference electrode, i.e., a common electrode, to supply the electric field to each one of the liquid crystal cells. Usually, each pixel electrode is formed for each liquid crystal cell on a lower substrate, while the common electrode is formed as an integrated whole on the entire surface of an upper substrate. Each pixel electrode connects to a thin film transistor (TFT) that is used as a switching element. The pixel electrode together with the common electrode drives the liquid crystal cell in response to data signals supplied via the TFT.
Referring to FIG. 1, there is shown a liquid crystal display panel in accordance with a related art, which includes upper and lower array substrates 10 and 20 combined together, and a liquid crystal material 8 between the upper and the lower array substrates 10 and 20.
The liquid crystal material 8 rotates, in response to an electric field supplied thereto, to thereby regulate the transmittance of incident light via the lower array substrate 20.
The upper array substrate 10 includes a color filter 4 and a common electrode 6 formed on a rear surface of the upper substrate 1. The color filter 4 includes color filters of red (R), green (G), and blue (B) and makes it possible to display colors by selectively passing light having a specific band of wavelength. A black matrix 2 is placed between the color filters 4 adjacent each other and prevents the degradation of the contrast ratio by absorbing the light incident from the adjacent cells.
The lower array substrate 20 includes: a data line 18 and a gate line 12, which cross each other and are insulated by a gate insulating layer, formed on the entire surface of the lower substrate 21; and a TFT 16 at the crossing of the data and the gate lines. The TFT 16 includes: a gate electrode connected to the gate line 12; a source electrode connected to the data line 18; and a drain electrode facing to the source electrode with a channel portion including an active layer and an ohmic contact layer therebetween. The TFT 16 is connected to the pixel electrode 14 via a contact hole passing through a passivation film. In response to gate signals from the gate line 12, the TFT 16 selectively supplies data signals from the data line 18 to the pixel electrode 14.
The pixel electrode 14 is made from a transparent conductive material having a high light transmittance and is in a cell region defined by the data line 18 and gate line 12. The pixel electrode 14 generates a potential difference along with a common electrode 6 by data signals supplied via the drain electrode. Under the influence of the potential difference, the liquid crystal material 8 between the upper and lower substrates 1 and 21 rotates due to the dielectric anisotropy thereof. Hence, the light supplied via the pixel electrode 14 from the light source passes toward the upper substrate 1.
The cell gap between the upper and the lower array substrates 10 and 20 is maintained by spacers and a liquid crystal material is injected in the space maintained by the spacers.
Meanwhile, the spacers for maintaining the cell gap are formed by a fabricating method shown FIGS. 2A to 2D.
First of all, as shown in FIG. 2A, mixed material of solvent, binder, monomer, and photo-initiator is printed and dried so as to evaporate the solvent, and then spacer material 26a, which is a mixture of binder, monomer and photo-initiator, is formed. Here, either the lower substrate having the TFT and the pixel electrode or the upper substrate having the color filter may be used as the substrate 11.
After a photo-resist 32 is applied on the substrate 11 having the spacer material 26a formed thereon, a photo mask MS is aligned as shown in FIG. 2B. The photo mask MS includes a mask substrate 34 having an exposure area S2 which is an exposed area, and a shielding layer 36 formed on the mask substrate 34 to have a shielding area S1.
By carrying out the exposure process to selectively irradiate ultraviolet rays to the photo-resist 32 using the photo mask MS and the development process to develop the exposed photo-resist, a photo-resist pattern 38 is formed as shown in FIG. 2C. The spacer material 26a is patterned through an etching process using the photo-resist pattern as a mask, and consequently, a pattern spacer having designated height is formed as shown in FIG. 2D.
The pattern spacer 26 of the related art LCD occupies only about 2% of the area of the substrate 11. More than 95% of the spacer material 26a that has been printed on the entire surface of the substrate 11 to form the pattern spacer 26 is removed during the processes of exposure, development, and etching. So, the spacer material is inadvertently wasted, and the costs of dedicated material and fabrication become high. Further, the additional mask process for forming the pattern spacer 26 including the processes such as printing, exposure, development, and etching leads to the problem that makes the fabricating process even more complex.
In order to solve these problems, a fabricating method for the spacer using an ink-jet device has been suggested as shown in FIGS. 3A to 3C.
First, as shown in FIG. 3A, an ink-jet device 40 is aligned so as to overlap with the location where the spacer is to be formed on the substrate 11. Here, either the lower substrate 21 having the TFT 16 and the pixel electrode 14 or the upper substrate having the color filter 4 may be used as the substrate 11.
Then, the spacer material 26a is dispensed onto the substrate 11 from the ink-jet device 40 as shown in FIG. 3B. In other words, when an external voltage is supplied to a piezoelectric element of an ink-jet head, physical pressure is generated. This physical pressure causes a conduit connecting a tank 42 containing the spacer material 26a with a nozzle to contract and relax repeatedly, and thereby the spacer material 26a is dispensed onto the substrate 11 through a nozzle 46.
The pattern spacer 26 formed by being dispensed the spacer material 26a through the nozzle 46 of the ink-jet device thereafter undergoes an exposure to the ultraviolet ray radiated from a light source 48 or a firing process as shown in FIG. 3C, and then comes to have designated width W and height H.
During the formation of the spacer using the related art ink-jet device, the spacer material 26a of low viscosity experiences gravity while being dispensed onto the substrate 11. Due to gravity, the spacer material 26a spreads out widely with undesirably small ratio of height H to width W when dispensed onto the substrate. This leads to the problem that the pattern spacer 26 that overlaps with the black matrix 2 encroaches on an area outside the black matrix 2, i.e., a display area and appears as a stain on the display area.